Featureflip Client SDK API

openapi: 3.2.0
info:
  title: Featureflip Evaluation Client SDK API
  description: High-performance feature flag evaluation service for SDKs
  version: v1
servers:
- url: https://eval.featureflip.io
  description: Production
security:
- Bearer: []
tags:
- name: Client SDK
  description: 'Client SDK endpoints for browser-side feature flag evaluation.

    All endpoints require a valid Client SDK key passed via the Authorization header.

    Unlike server SDK endpoints, these evaluate flags server-side and return only values.'
paths:
  /v1/client/evaluate:
    post:
      tags:
      - Client SDK
      summary: Evaluates all client-visible feature flags for the given user context
      requestBody:
        description: The evaluation request containing user context attributes.
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
          text/json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
          application/*+json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
      responses:
        '200':
          description: Returns the evaluation results for all client-visible flags.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ClientEvaluateResponse'
        '401':
          description: Client SDK key is missing or invalid.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ProblemDetails'
        '503':
          description: Flag configuration is temporarily unavailable; retry after the interval in `Retry-After`.
      operationId: postV1ClientEvaluate
      x-operation-id-source: derived
  /v1/client/identify:
    post:
      tags:
      - Client SDK
      summary: Re-identifies the user with a new context, for example after login
      description: 'Re-evaluates all client-visible flags and returns the updated values. Also updates the

        context on any active SSE connections for this environment.'
      requestBody:
        description: The evaluation request containing the new user context attributes.
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
          text/json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
          application/*+json:
            schema:
              $ref: '#/components/schemas/ClientEvaluateRequest'
      responses:
        '200':
          description: Returns the re-evaluated results for all client-visible flags.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ClientEvaluateResponse'
        '401':
          description: Client SDK key is missing or invalid.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ProblemDetails'
        '503':
          description: Flag configuration is temporarily unavailable; retry after the interval in `Retry-After`.
      operationId: postV1ClientIdentify
      x-operation-id-source: derived
  /v1/client/stream:
    get:
      tags:
      - Client SDK
      summary: Opens a Server-Sent Events stream for real-time client flag updates
      description: 'Auth is passed as an `?authorization=csk_...` query parameter because a browser

        EventSource cannot set headers. User context is passed as `?context=base64json`.'
      parameters:
      - name: context
        in: query
        description: Base64-encoded JSON user context for flag evaluation.
        schema:
          type: string
      responses:
        '200':
          description: SSE stream opened successfully.
        '401':
          description: Client SDK key is missing or invalid.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ProblemDetails'
        '503':
          description: Flag configuration is temporarily unavailable; retry after the interval in `Retry-After`.
      operationId: getV1ClientStream
      x-operation-id-source: derived
components:
  schemas:
    ProblemDetails:
      type: object
      properties:
        type:
          type:
          - string
          - 'null'
        title:
          type:
          - string
          - 'null'
        status:
          type:
          - integer
          - 'null'
          format: int32
        detail:
          type:
          - string
          - 'null'
        instance:
          type:
          - string
          - 'null'
      additionalProperties: {}
    ClientEvaluateRequest:
      required:
      - context
      type: object
      properties:
        context:
          type:
          - object
          - 'null'
          additionalProperties: {}
      additionalProperties: false
    ClientEvaluateResponse:
      required:
      - flags
      type: object
      properties:
        flags:
          type:
          - object
          - 'null'
          additionalProperties:
            $ref: '#/components/schemas/ClientFlagValue'
      additionalProperties: false
    ClientFlagValue:
      required:
      - reason
      - value
      - variation
      type: object
      properties:
        value: {}
        variation:
          type:
          - string
          - 'null'
        reason:
          type:
          - string
          - 'null'
        prerequisiteKey:
          type:
          - string
          - 'null'
      additionalProperties: false
  securitySchemes:
    Bearer:
      type: apiKey
      description: SDK Key authorization. Enter your SDK key.
      name: Authorization
      in: header